Pelvic disorder treatment device

ABSTRACT

A device ( 20 ) for treating a medical condition is provided, and a surgical procedure for implanting the device is disclosed. The device ( 20 ) includes a sensor ( 44 ), which is adapted to generate a signal responsive to a state of a patient, and at least one electrode ( 27 ), which is adapted to be coupled to a pelvic site of the patient. A control unit ( 22 ) is adapted to receive the signal, to analyze the signal so as to distinguish between an imminent stress incontinence event and an imminent urge event, and, responsive to analyzing the signal, to apply an electrical waveform to the at least one electrode ( 27 ). In various configurations, the device ( 20 ) may be used alternatively or additionally to treat fecal incontinence, interstitial cystitis, chronic pelvic pain, or urine retention.

CROSS-REFERENCE TO RELATED APPLICATION

The present patent application is a US national phase application of PCTPatent Application PCT/IL02/00963, entitled, “Pelvic disorder treatmentdevice,” filed Nov. 28, 2002. The PCT application is acontinuation-in-part of U.S. patent application Ser. No. 09/996,668,filed Nov. 29, 2001, now U.S. Pat. No. 6,862,480 also entitled, “Pelvicdisorder treatment device,” and is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to electronic medical devices,and specifically to devices to relieve problems associated with urinaryincontinence and other pelvic disorders.

BACKGROUND OF THE INVENTION

Urinary incontinence affects millions of people, causing discomfort andembarrassment, sometimes to the point of social isolation. In the UnitedStates, recent studies have shown that as many as 25 million persons, ofwhom approximately 85% are women, are affected by bladder controlproblems. Incontinence occurs in children and young adults, but thelargest number affected are the elderly.

There are several major forms of incontinence:

-   -   Stress incontinence is an involuntary loss of urine while doing        physical activities which put pressure on the abdomen. These        activities include exercise, coughing, sneezing, laughing,        lifting, or any body movement which puts pressure on the        bladder. Stress incontinence is typically associated with either        or both of the following anatomical conditions:

Urethral hypermobility—Weakness of or injury to pelvic floor musclescauses the bladder to descend during abdominal straining or pressure,allowing urine to leak out of the bladder. This is the more commonsource of stress incontinence.

Intrinsic sphincter deficiency—In this condition, the urethralmusculature is unable to completely close the urethra or keep it closedduring stress.

-   -   Urge incontinence is the sudden urgent need to pass urine, and        is caused by a sudden bladder contraction that cannot be        consciously inhibited. This type of incontinence is not uncommon        among healthy people, and may be linked to disorders such as        infections that produce muscle spasms in the bladder or urethra.        Urge incontinence may also result from illnesses that affect the        central nervous system.    -   Overflow incontinence refers to leakage of urine that occurs        when the quantity of urine exceeds the bladder's holding        capacity, typically as a result of a blockage in the lower        urinary tract.    -   Reflex incontinence is the loss of urine when the person is        unaware of the need to urinate. This condition may result from        nerve dysfunction, or from a leak in the bladder, urethra, or        ureter.

Of the major forms of incontinence listed above, the two most common arestress and urge. “Mixed incontinence” is a term used to describe thecommon phenomenon of the presence of stress and urge incontinence in thesame patient.

A large variety of products and treatment methods are available for careof incontinence. Most patients suffering from mild to moderateincontinence use diapers or disposable absorbent pads. These productsare not sufficiently absorbent to be effective in severe cases, areuncomfortable to wear, and can cause skin irritation as well asunpleasant odors. Other non-surgical products for controllingincontinence include urethral inserts (or plugs), externally wornadhesive patches, and drugs.

Exercise and behavioral training are also effective in some cases inrehabilitating pelvic muscles and thus reducing or resolvingincontinence. Patients are taught to perform Kegel exercises tostrengthen their pelvic muscles, which may be combined with electricalstimulation of the pelvic floor. Electromyographic biofeedback may alsobe provided to give the patients an indication as to the effectivenessof their muscular exertions. But retraining muscles is not possible orfully effective for most patients, particularly when there may beneurological damage or when other pathologies may be involved.

Medtronic Neurological, of Columbia Heights, Minn., produces a deviceknown as Interstim, for treatment of urge incontinence. Interstim usesan implantable pulse generator, which is surgically implanted in thelower abdomen and wired to nerves near the sacrum (the bone at the baseof the spine) in a major surgical procedure—sometimes six hours undergeneral anesthesia. Electrical impulses are then transmittedcontinuously to a sacral nerve that controls urinary voiding. Thecontinuous electrical stimulation of the nerve has been found to controlurge incontinence in some patients.

Various surgical procedures have been developed for bladder necksuspension, primarily to control urethral hypermobility by elevating thebladder neck and urethra. These procedures typically use bone anchorsand sutures or slings to support the bladder neck. The success rates forbladder neck suspension surgery in controlling urinary leakage aretypically approximately 60%-80%, depending on the patient's condition,the surgeon's skill, and the procedure which is used. The disadvantagesof this surgical technique are its high cost, the need forhospitalization and long recovery period, and the frequency ofcomplications.

For serious cases of intrinsic sphincter deficiency, artificial urinarysphincters have been developed. For example, the AMS 800 urinarysphincter, produced by American Medical Systems Inc., of Minnetonka,Minn., includes a periurethral inflatable cuff, which is used toovercome urinary incontinence when the function of the natural sphincteris impaired. The cuff is coupled to a manually-operated pump and apressure regulator chamber, which are implanted in a patient's bodytogether with the cuff. The cuff is maintained at a constant pressure of60-80 cm of water, which is generally higher than the bladder pressure.To urinate, the patient releases the pressure in the cuff. Aspects ofthis system are described in U.S. Pat. No. 4,222,377 to Burton, which isincorporated herein by reference.

This artificial sphincter has several shortcomings, however. Theconstant concentric pressure that the periurethral cuff exerts on theurethra can result in impaired blood supply to tissue in the area,leading to tissue atrophy, urethral erosion and infection. Furthermore,the constant pressure in the cuff is not always sufficient to overcometransient increases in bladder pressure that may result from straining,coughing, laughing or contraction of the detrusor muscle. In such cases,urine leakage may result.

U.S. Pat. Nos. 4,571,749 and 4,731,083 to Fischell, which areincorporated herein by reference, describe an artificial sphincterdevice whose pressure can vary in response to changes in abdominal orintravesical (bladder) pressure. The device includes a periurethralcuff, subdermic pump, pressure regulator, and hydraulic pressure sensor.

U.S. Pat. No. 3,628,538 to Vincent et al., which is incorporated hereinby reference, describes apparatus for stimulating a muscle based on anelectromyographic (EMG) signal sensed in the muscle. If the signal isgreater than a predetermined threshold value, a stimulator circuitapplies a voltage to electrodes adjacent to the muscle. The apparatus issaid to be particularly useful in overcoming incontinence.

U.S. Pat. No. 6,135,945 to Sultan, which is incorporated herein byreference, describes apparatus for preventing uncontrolled discharge ofurine from a patient's urethra. The apparatus includes an implantablepressure sensor for sensing intra-abdominal pressure, which generates apressure signal in response to the sensed pressure. An actuating deviceis coupled to the pressure sensor, and generates an electrical signal inresponse to the pressure signal. A controller is coupled to theactuating device, and is configured to selectively compress thepatient's urethra and thereby prevent incontinence.

Various types of electrodes have been proposed for applying electricalstimulation to pelvic muscles so as to prevent unwanted urine flow. Forexample, U.S. Pat. No. 5,562,717 to Tippey et al. describes electrodesthat are placed on the body surface, typically in the areas of theperineum and the sacrum, and are electrically actuated to controlincontinence. U.S. Pat. No. 4,785,828 to Maurer describes a vaginal plughaving electrodes on an outer surface thereof. A pulse generator in theplug applies electrical pulses to the electrodes so as to constrict thepatient's pelvic muscles and prevent urine flow. U.S. Pat. No. 4,153,059to Fravel et al. describes an intra-anal electrode, to which repetitiveelectrical pulses are applied in order to control urinary incontinence.U.S. Pat. No. 4,106,511 to Erlandsson describes an electrical stimulatorin the form of a plug for insertion into the vagina or the anus. U.S.Pat. No. 3,866,613 to Kenny et al. describes a pessary ring having twoelectrodes thereon, which are energized to control incontinence. U.S.Pat. No. 4,406,288 to Horwinski et al. describes apparatus forconditioning the pelvic floor musculature to reduce bladdercontractility and relax the bladder, so as to prevent involuntaryurinary loss. All of the above-mentioned patents are incorporated hereinby reference.

U.S. Pat. No. 4,580,578 to Barson, which is incorporated herein byreference, describes a device for stimulating the sphincter musclescontrolling the bladder. A supporting body is fitted into the patient'svulva between the labia, so that two electrodes attached to thesupporting body contact the epidermal surface on either side of theexternal urethral orifice. Electrical impulses are applied to theelectrodes to stimulate the region of the sphincter.

U.S. Pat. No. 4,607,639 to Tanagho et al., which is incorporated hereinby reference, describes a method for controlling bladder function bynerve stimulation, typically of a sacral nerve. The anatomical locationof at least one nerve controlling the muscles for the bladder and/or itssphincter is identified, and an electrode is placed on the nerve toselectively stimulate the nerve for continence and evacuation purposes.

U.S. Pat. No. 4,739,764 to Lue et al., which is incorporated herein byreference, describes a system for electrical stimulation of nerves inorder to treat urinary incontinence, fecal incontinence, interstitialcystitis, and other pelvic pain syndromes.

U.S. Pat. No. 6,240,315 to Mo et al., which is incorporated herein byreference, describes incontinence treatment apparatus which includes amodule for evaluating a recorded EMG signal.

U.S. Pat. No. 5,484,445 to Knuth, which is incorporated herein byreference, describes a system for anchoring a lead to the sacrum forpurposes of long-term stimulation, typically for treatment ofincontinence.

U.S. Pat. Nos. 5,927,282 and 6,131,575 to Lenker et al., which areincorporated herein by reference, describe removable external closuresfor the urethra as means for relieving or mitigating incontinenceproblems.

U.S. Pat. No. 6,002,964 to Feler et al., which is incorporated herein byreference, describe a method for managing chronic pelvic pain. Themethod includes techniques for positioning one or more stimulation leadswithin or about the sacrum to enable electrical energy to be applied tospinal nervous tissue, including nerve roots, in order to inhibit thetransmission of pain signals.

An article by Fall et al., entitled, “Electrical stimulation ininterstitial cystitis,” Journal of Urology, 123(2), pp. 192-195, Feb.1980, which is incorporated herein by reference, describes a study inwhich fourteen women with chronic interstitial cystitis were treatedwith long-term intravaginal or transcutaneous nerve stimulation.Clinical and urodynamic evaluations were performed after 6 months to 2years. Improvement was not immediate, but required a considerable periodof continuous, daily use of electrical stimulation.

An article by Zermann et al., entitled, “Sacral nerve stimulation forpain relief in interstitial cystitis,” Urol. Int., 65(2), pp. 120-121,2000, which is incorporated herein by reference, describes a case inwhich a 60-year-old woman was treated for severe interstitial cystitispain using sacral nerve stimulation.

An article by Chai et al., entitled, “Percutaneous sacral third nerveroot neurostimulation improves symptoms and normalizes urinary HB-EGFlevels and antiproliferative activity in patients with interstitialcystitis,” Urology, 55(5), pp. 643-646, May, 2000, which is incorporatedherein by reference, notes: “A highly effective treatment forinterstitial cystitis (IC) remains elusive. . . . Results suggest thatpermanent S3 PNS may be beneficial in treating IC.”

An article by Caraballo et al., entitled, “Sacral nerve stimulation as atreatment for urge incontinence and associated pelvic floor disorders ata pelvic floor center: a follow-up study,” Urology, 57(6 Suppl 1), p.121, June, 2001, which is incorporated herein by reference, describesand presents the results of an additional study in which sacral nervestimulation was applied in an effort to treat urinary incontinence.

PCT Patent Publication WO 00/19939, entitled, “Control of urgeincontinence,” which is assigned to the assignee of the present patentapplication and incorporated herein by reference, describes a device fortreatment of urinary urge incontinence, in which imminent urgeincontinence is sensed, and a pelvic nerve or muscle is stimulated toinhibit the flow.

PCT Patent Publication WO 00/19940, entitled, “Incontinence treatmentdevice,” which is assigned to the assignee of the present patentapplication and incorporated herein by reference, describes a device fortreating urinary stress incontinence, in which imminent involuntaryurine flow is sensed, and a pelvic nerve or muscle is stimulated toinhibit the flow.

A book entitled Urinary Incontinence, edited by P. O'Donnell, MosbyPublishers, 1997, which is incorporated herein by reference, describesclinical aspects relating to the diagnosis and treatment of urinaryincontinence.

SUMMARY OF THE INVENTION

It is an object of some aspects of the present invention to providedevices and methods for treating mixed incontinence.

It is a further object of some aspects of the present invention toprovide improved devices and methods for relieving pelvic pain.

It is yet a further object of some aspects of the present invention toprovide improved devices and methods for treating fecal incontinence.

It is yet a further object of some aspects of the present invention toprovide improved devices and methods for treating urine retention.

It is still a further object of some aspects of the present invention toprovide improved methods for implanting pelvic electrical apparatus.

In preferred embodiments of the present invention, a device fortreatment of both urinary stress incontinence and urge incontinencecomprises a control unit, one or more electrodes coupled to the controlunit, and one or more sensors, also coupled to the control unit. Theelectrodes are preferably implanted in the pelvic region of a patient soas to be in electrical contact with one or more of the muscles or nervesthat are used in regulating urine flow from the bladder. The controlunit is preferably implanted under the skin of the abdomen or genitalregion, and receives signals from the electrodes and/or from thesensors. Motion, pressure and/or electromyographic (EMG) signalsconveyed by the electrodes or sensors are analyzed by the control unit,as described hereinbelow, in order to distinguish between signalsindicative of urge incontinence and those indicative of stressincontinence. When the control unit determines that the signals areindicative of impending urge incontinence, it drives the electrodes toapply a signal having parameters configured to treat urge incontinence.When, however, the control unit determines that the signals areindicative of stress incontinence, it drives the electrodes to apply asignal having parameters that are configured to treat stressincontinence. As appropriate, the control unit may also configure thecurrent applied by the electrodes so as to treat other disorders, suchas fecal incontinence, interstitial cystitis, urine retention, or othersources of pelvic dysfunction, pain or discomfort.

It is to be appreciated that, in the context of the present patentapplication and in the claims, treatments described for inhibiting“imminent” conditions such as an event of stress incontinence which isexpected to occur, may also be applied to inhibit a presently-occurringcondition, such as involuntary voiding due to stress incontinence.

In addition, it is to be appreciated that although some preferredembodiments of the present invention are described herein with respectto treating urge incontinence, the scope of the present inventionincludes treating other urge “events” as well. For example, urge eventssuch as urge frequency (the excessively frequent sensation of veryimminent voiding, in patients who do not necessarily experienceincontinence following such sensations, also known in the art as urgencyfrequency) or neurogenic bladder conditions are preferably treated usingidentical protocols as those described herein for the treatment of urgeincontinence, or protocols analogous to those described herein for thetreatment of urge incontinence, mutatis mutandis.

Preferably, the control unit is programmed to distinguish betweensignals indicative of possible incontinence and other signals that donot warrant stimulation of the muscles. In particular, the control unitis preferably programmed to recognize signal patterns indicative ofnormal voiding, and, consequently, does not stimulate the muscles whensuch patterns occur.

Typically, devices in accordance with preferred embodiments of thepresent invention actuate the electrodes to treat urge or stressincontinence only when physiological or other signals indicate that suchtreatment is needed. At other times, stimulation is generally notapplied. Implantation of the device provides reliable, typicallylong-term control of muscle function, and relieves incontinence or otherpelvic disorders in a manner that is unobtrusive and minimizesinconvenience and discomfort of the patient. By contrast, many prior artelectrical devices for treating pelvic disorders are not implanted orintended for long-term use, but are instead intended for temporary use,e.g., to train pelvic muscles via a device incorporated in a vaginalplug. These prior art devices are typically removed after a relativelyshort treatment period.

Numerous benefits are obtained, according to these embodiments, byactuating the electrodes only “on-demand,” i.e., only when possibleimminent stress or urge incontinence is detected. For example, musclefatigue and nerve irritation—both phenomena being associated withcontinuous excitation—are typically reduced or eliminated according tothese embodiments. Accordingly, power consumption is reduced, andbattery life is thereby increased.

Preferably, the electrodes are implanted so as to stimulate muscles ofthe pelvic floor. Alternatively or additionally, one or more of theelectrodes may be implanted in or adjacent to the detrusor muscle or ina position suitable for stimulating a nerve, such as the sacral nerve,as described in the above-mentioned U.S. Pat. No. 4,607,639, forexample, or in one or more of the other references cited in theBackground section of the present patent application.

In some preferred embodiments of the present invention, the one or moreelectrodes comprise a single electrode, which both receives the EMGsignals and applies the stimulation waveform. Alternatively, separatesensing and stimulation electrodes may be used.

In some preferred embodiments of the present invention, the sensorscomprise one or more mechanical sensors, such as pressure, force, motionor acceleration sensors, or an ultrasound transducer, which arepreferably implanted on, in or in the vicinity of the bladder. Thesesensors preferably generate signals responsive to motion, tointravesical or abdominal pressure, or to urine volume in the bladder,and are thus indicative of possible imminent incontinence. The controlunit processes the signals from the sensors in order to determinewhether and what type of electrical stimulation should be applied.

In a preferred embodiment of the present invention, the patient herselfinstructs the control unit to initiate stimulation of the muscles. Forexample, the patient may input the instruction to the control unit byvoluntarily tightening her abdominal muscles, which in turn causesmeasurable increases in abdominal pressure. Typically, this is done whenthe patient senses imminent urge incontinence. The control unitdistinguishes the voluntary contraction from other sources of pressurechanges responsive to the rate of change of the measured pressure.Alternatively or additionally, the control unit comprises an externalinput unit, such as a keypad, through which the patient entersinstructions. For some applications, the patient is further enabled toindicate to the control unit that she feels imminent stressincontinence, e.g., shortly prior to sneezing.

In a preferred embodiment of the present invention, the processor isprogrammable after implantation of the device, most preferably by meansof a wireless communications link, so that the strength and shape of thestimulation waveform and the response of the device to theelectromyographic and/or other physiological signals can be adjusted inresponse to the patient's clinical characteristics and experience withthe device. The wireless link can preferably also be used by the patientto turn the device on or off. Such methods of signal processing,programming and control, as well as other useful methods and apparatus,are described in U.S. patent application Ser. No. 09/413,272, entitled“Incontinence Treatment Device,” which is assigned to the assignee ofthe present patent application and incorporated herein by reference.

There is therefore provided, in accordance with a preferred embodimentof the present invention, a device, including:

a sensor, which is adapted to generate a signal responsive to a state ofa patient;

at least one electrode, which is adapted to be coupled to a pelvic siteof the patient; and

a control unit, which is adapted to receive the signal, to analyze thesignal so as to distinguish between an imminent stress incontinenceevent and an imminent urge event, and, responsive to analyzing thesignal, to apply an electrical waveform to the at least one electrode.

In a preferred embodiment, the at least one electrode includes a singleelectrode adapted to be coupled to the pelvic site, wherein the controlunit is adapted to apply a first waveform to the single electroderesponsive to determining that a stress incontinence event is imminent,and wherein the control unit is adapted to apply to the single electrodea second waveform, different from the first waveform, responsive todetermining that an urge event is imminent.

Typically, the control unit is adapted to analyze the signal so as todistinguish between the imminent stress incontinence event and animminent urge incontinence event. Alternatively or additionally, thecontrol unit is adapted to analyze the signal so as to distinguishbetween the imminent stress incontinence event and an urge-frequencyevent.

In a preferred embodiment, the control unit is adapted to receive aninput from the patient and to apply the waveform responsive to theinput.

For some applications, the at least one electrode is adapted to beimplanted so as to stimulate a nerve in the pelvic region of thepatient. Alternatively or additionally, the at least one electrode isadapted to be implanted in contact with a pelvic muscle of the patient.

In a preferred embodiment, the at least one electrode includes:

a first electrode, adapted to be coupled to a first pelvic site; and

a second electrode, adapted to be coupled to a second pelvic site,

wherein the control unit is adapted to apply a first waveform to thefirst electrode responsive to analyzing the signal and determining thata stress incontinence event is imminent, and wherein the control unit isadapted to apply to the second electrode a second waveform, differentfrom the first waveform, responsive to determining that an urge event isimminent.

In this case, the first electrode is often adapted to be coupled to apelvic muscle of the patient, while the second electrode is adapted tobe coupled to a sacral nerve of the patient.

Preferably, the control unit is adapted to configure the waveform so asto stimulate a pelvic muscle to contract so as to inhibit involuntaryurine flow through the patient's urethra. Typically, the control unit isadapted to configure the waveform so as to stimulate the pelvic muscleto contract responsive to analyzing the signal and determining that astress incontinence event is imminent. Moreover, the control unit ispreferably adapted to configure the waveform to have (a) a frequencycomponent between about 40 and 50 Hz, (b) an amplitude between about 3and 9 V, (c) a series of pulses having widths between about 0.05 and 1ms, and/or a duration between about 0.2 and 1 second, responsive todetermining that a stress incontinence event is imminent.

In a preferred embodiment, the control unit is adapted to configure thewaveform so as to induce relaxation of a bladder muscle of the patient.Typically, the control unit is adapted to configure the waveform so asto induce the relaxation of the bladder muscle responsive to analyzingthe signal and determining that an urge event is imminent. In this case,the control unit is preferably adapted to configure the waveform to have(a) a frequency component between about 5 and 15 Hz, (b) a duration lessthan about 10 minutes, (c) an amplitude between about 0.5 and 5 V,and/or (d) a series of pulses having widths between about 0.05 and 1 ms,responsive to determining that an urge event is imminent. For someapplications, the control unit is adapted to configure the waveform toinclude a rise time lasting between about 1 second and 1 minute prior toattaining a designated waveform application voltage, responsive todetermining that an urge event is imminent. Alternatively oradditionally, the control unit is adapted to configure the waveform toinclude a decay time lasting between about 1 second and 1 minute priorto returning to a baseline voltage, responsive to determining that anurge event is imminent.

In a preferred embodiment, the control unit is adapted to configure thewaveform to have a duty cycle between about 5% and 15%, responsive todetermining that an urge event is imminent. In a preferred embodiment,the control unit is adapted to configure the waveform to have a dutycycle between about 6% and about 50%. In a preferred embodiment, thecontrol unit is adapted to configure the wavefonn to have a duty cycleof between about 2 and about 10 seconds on, and between about 10 andabout 30 seconds off.

For some applications, the sensor includes a sensing electrode adaptedto sense electrical activity of a bladder muscle of the patient.Preferably, but not necessarily, the at least one electrode includes thesensing electrode, and the control unit is adapted to apply the waveformto the sensing electrode responsive to analyzing the signal.

Typically, the sensor includes a pressure sensor, and the control unitis adapted to analyze a rate of change of the received signal, toidentify the imminent stress incontinence event responsive to arelatively high rate of change of the received signal, and to identifythe imminent urge event responsive to a relatively low rate of change ofthe received signal. In a preferred embodiment, the sensor is adapted tobe implanted at an abdominal site of the patient, and the sensor isadapted to generate the signal with a relatively low rate of changeresponsive to voluntary contraction by the patient of abdominalmusculature of the patient.

In a preferred application, the control unit is adapted to evaluate theimminence of the urge event responsive to an amount of time elapsedsince the patient last voided.

Preferably, the sensor is adapted to be coupled to the patient'sbladder, and includes a pressure sensor, an acceleration sensor, and/oran ultrasound transducer.

There is also provided, in accordance with a preferred embodiment of thepresent invention, a device, including:

a first sensor, which is adapted to be coupled to a bladder site of apatient and to generate a first signal, responsive to a pressure in thebladder;

a second sensor, which is adapted to be coupled to an abdominal site ofthe patient and to generate a second signal, responsive to an overallpressure in the abdomen;

at least one electrode, which is adapted to be coupled to a pelvic siteof the patient; and

a control unit, which is adapted to receive the first and secondsignals, analyze the signals so as to distinguish between two conditionsof the patient, and apply an electrical waveform to the at least oneelectrode, responsive to analyzing the signals.

Preferably, the first sensor includes a first pressure sensor, andwherein the second sensor includes a second pressure sensor.

In a preferred embodiment, the control unit is adapted to: (a) analyzethe first and second signals so as to detect a characteristic in thefirst signal and a characteristic in the second signal, (b) identifywhether the characteristic in the first signal is a significant changethereof and whether the characteristic in the second signal is asignificant change thereof that generally corresponds in time to thechange in the first signal, and (c) configure the waveform responsive tostep (b).

Alternatively or additionally, the control unit is adapted to: (a)analyze the first and second signals so as to detect a characteristic inthe first signal and a characteristic in the second signal, (b) identifywhether the characteristic in the first signal is a significant changethereof and whether the characteristic in the second signal is asignificant change thereof that generally corresponds in time to thechange in the first signal, (c) apply a first waveform to the at leastone electrode if the analysis identifies the change in the first signalas generally corresponding in time to the change in the second signal,and (d) apply to the at least one electrode a second waveform, differentfrom the first waveform, if the analysis identifies the change in thefirst signal as not generally corresponding in time to the change in thesecond signal. In this case, the control unit is preferably adapted toconfigure the first waveform for treatment of stress incontinence of thepatient, and wherein the control unit is adapted to configure the secondwaveform for treatment of an urge disorder of the patient.

There is further provided, in accordance with a preferred embodiment ofthe present invention, a device, including:

a sensor, which is adapted to generate a signal responsive to a state ofa patient;

at least one electrode, which is adapted to be coupled to a pelvic siteof the patient; and

a control unit, which is adapted to receive the signal, to analyze thesignal so as to determine a likelihood of imminent fecal incontinence,and, responsive to analyzing the signal, to apply an electrical waveformto the at least one electrode.

Preferably, the control unit is adapted to configure the waveform so asto stimulate an anal sphincter muscle to contract. Alternatively oradditionally, the at least one electrode is adapted to be implanted soas to stimulate a nerve in the pelvic region of the patient. In apreferred embodiment, the at least one electrode is adapted to beimplanted in contact with a pelvic muscle of the patient.

The control unit is preferably adapted to configure the waveform to have(a) a frequency component between about 40 and 50 Hz, (b) an amplitudebetween about 3 and 9 V, (c) a series of pulses having widths betweenabout 0.05 and 1 ms, and/or (d) a duration between about 1 and 20seconds.

Preferably, the at least one electrode includes a single monopolarelectrode and/or at least one electrode includes a pair of bipolarelectrodes. The at least one electrode typically includes a flexibleintramuscular electrode.

In a preferred embodiment, the at least one electrode and the controlunit are adapted to be implanted in the body of the patient.

In a preferred embodiment, the control unit is adapted to receive aninput from the patient and to apply the waveform responsive to theinput.

For some applications, the control unit is adapted to analyze the signalso as to distinguish between: (a) a first signal, indicative of imminentfecal incontinence, and (b) a second signal, indicative of voluntaryvoiding by the patient. For example, the control unit may be adapted todistinguish between the first and second signals responsive to a rate ofchange of the signal generated by the sensor. Alternatively oradditionally, the control unit is adapted to gather informationregarding the signal over an extended period and to analyze theinformation to find a pattern characteristic of the patient, for use indetermining when imminent fecal incontinence is likely. In this case,the control unit is typically adapted to associate with the pattern atime-varying threshold to which a level of the signal is compared.

Typically, the sensor is adapted to be implanted at a pelvic location ofthe patient, and includes a pressure sensor, an acceleration sensor, anultrasound transducer, and/or a sensing electrode. In a preferredembodiment, the sensor includes the at least one electrode.

For some applications, the sensor is adapted to generate the signalresponsive to a level of filling of the rectum of the patient, and thecontrol unit is adapted to apply the waveform to the at least oneelectrode responsive to the signal. In this case, the sensor typicallyincludes a pressure sensor. Preferably, the control unit is adapted toincrease a parameter of the waveform responsive to a level of thesignal. Further preferably, the control unit is adapted to configure thewaveform to be such as to induce afferent signaling in the patient,e.g., to be such as to induce in the patient afferent signaling of aform which induces a conscious sensation of rectal filling. In thislatter case, the control unit is typically adapted to configure thewaveform to be such as to induce in the patient afferent signaling of aform which induces a conscious sensation of rectal filling and an urgeto voluntarily contract an anal sphincter muscle of the patient.Alternatively or additionally, the control unit is adapted to configurethe waveform to be such as to induce afferent signaling in the patientof a form that induces contraction of a smooth muscle in a pelvic regionof the patient and inhibits fecal incontinence.

There is yet further provided, in accordance with a preferred embodimentof the present invention, a device, including:

at least one electrode, which is adapted to be coupled to a pelvicmuscle of a patient; and

a control unit, which is adapted to drive the at least one electrode toapply to the muscle an electrical waveform configured to reduce patientpain due to interstitial cystitis.

For some applications, the control unit is adapted to receive an inputfrom the patient and to apply the waveform responsive to the input.Alternatively or additionally, the control unit is adapted to drive theat least one electrode responsive to an amount of time elapsed since thepatient last voided.

The control unit is typically adapted to configure the waveform so as toinduce relaxation of a bladder muscle of the patient.

In a preferred embodiment, the control unit is adapted to configure thewaveform to have (a) a frequency component between about 5 and 15 Hz,(b) an amplitude between about 1 and 4 V, (c) a series of pulses havingwidths between about 0.05 and 0.2 ms, and/or (d) a duration of about10-30 minutes. Alternatively or additionally, the control unit isadapted to configure the waveform to include a rise time lasting betweenabout 1 second and 3 minutes prior to attaining a designated waveformapplication voltage. Further alternatively or additionally, the controlunit is adapted to configure the waveform to include a decay timelasting between about 1 second and 3 minutes, prior to returning to abaseline voltage.

For some applications, the control unit is adapted to configure thewaveform to have a duty cycle between about 5% and 15%. For someapplications, the control unit is adapted to configure the waveform tohave a duty cycle between about 6% and about 50%. For some applications,the control unit is adapted to configure the waveform to have a dutycycle of between about 2 and about 10 seconds on, and between about 10and about 30 seconds off.

There is still further provided, in accordance with a preferredembodiment of the present invention, a device, including:

a sensor, which is adapted to generate a signal responsive to a state ofa patient;

at least one electrode, which is adapted to be coupled to an anatomicalsite of the patient; and

a control unit, which is adapted to receive the signal, to analyze thesignal so as to determine a likelihood of imminent patient pain due tointerstitial cystitis, and, responsive to analyzing the signal, to applyto the at least one electrode an electrical waveform configured toreduce patient pain due to interstitial cystitis.

For some applications, the sensor includes a sensing electrode adaptedto sense electrical activity of a bladder muscle of the patient.

Alternatively or additionally, the control unit is adapted to evaluatethe imminence of the interstitial cystitis responsive to an amount oftime elapsed since the patient last voided.

In a preferred embodiment, the control unit is adapted to receive anindication of a fill level of the patient's bladder and to inhibitapplication of the electrical waveform when the fill level of thebladder is low.

Preferably, the control unit is adapted to analyze the signal so as todistinguish between: (a) a first signal, indicative of imminentinterstitial cystitis, and (b) a second signal, indicative of voluntaryvoiding by the patient. For example, the control unit may be adapted todistinguish between the first and second signals responsive to a rate ofchange of the signal generated by the sensor. Alternatively oradditionally, the control unit is adapted to gather informationregarding the signal over an extended period and to analyze theinformation to find a pattern characteristic of the patient, for use indetermining when imminent interstitial cystitis is likely. In this case,the control unit is preferably adapted to associate with the pattern atime-varying threshold to which a level of the signal is compared.

In a preferred embodiment, the sensor includes a pressure sensor, andthe control unit is adapted to analyze a rate of change of the receivedsignal, and to identify the imminent interstitial cystitis responsive toa low rate of change of the received signal.

In a preferred application, the sensor is adapted to be implanted at anabdominal site of the patient, and the sensor is adapted to generate thesignal with a low rate of change responsive to voluntary contraction bythe patient of abdominal musculature of the patient.

Typically, but not necessarily, the sensor is adapted to be coupled tothe patient's bladder, and comprises a pressure sensor, an accelerationsensor, and/or an ultrasound transducer.

Preferably, the at least one electrode and the control unit are adaptedto be implanted in the body of the patient. In this case, the at leastone electrode is adapted to be implanted so as to stimulate a nerve inthe pelvic region of the patient. Alternatively or additionally, the atleast one electrode is adapted to be implanted in contact with a pelvicmuscle of the patient.

There is additionally provided, in accordance with a preferredembodiment of the present invention, a device, including:

at least one electrode, which is adapted to be coupled to a pelvicmuscle of a patient; and

a control unit, which is adapted to drive the at least one electrode toapply to the muscle an electrical waveform configured to reduce patientpelvic pain.

There is still additionally provided, in accordance with a preferredembodiment of the present invention, a device, including:

a sensor, which is adapted to generate a signal responsive to a state ofa patient;

at least one electrode, which is adapted to be coupled to an anatomicalsite of the patient; and

a control unit, which is adapted to receive the signal, to analyze thesignal so as to determine a likelihood of patient pelvic pain, and,responsive to analyzing the signal, to apply to the at least oneelectrode an electrical waveform configured to reduce the patient pelvicpain.

These devices for reducing patient pelvic pain are preferably configuredto be similar to the devices for treating interstitial cystitisdescribed herein.

There is yet additionally provided, in accordance with a preferredembodiment of the present invention, a device, including:

a sensor, which is adapted to generate a signal responsive to a pressureat an abdominal site of a patient;

at least one electrode, which is adapted to be coupled to an anatomicalsite of the patient; and

a control unit, which is adapted to receive the signal, to analyze acharacteristic of the signal so as to identify a voluntary contractionof abdominal musculature of the patient that indicates an onset of apelvic condition of the patient, and, responsive to analyzing thesignal, to apply to the at least one electrode an electrical waveformconfigured to inhibit the condition.

Preferably, the sensor includes a pressure sensor, and the control unitis adapted to analyze a rate of change of the received signal, and toidentify the voluntary contraction responsive to a low rate of change ofthe received signal.

There is also provided, in accordance with a preferred embodiment of thepresent invention, a device, including:

at least one electrode, which is adapted to be implanted at a pelvicmuscle site of a patient; and

a control unit, which is adapted to drive the at least one electrode toapply to the muscle an electrical waveform configured to inhibit urineretention of the patient.

Typically, but not necessarily, the control unit is adapted to receivean input from the patient and to apply the waveform responsive to theinput.

The control unit is preferably adapted to configure the waveform to have(a) a frequency component between about 1 and 10 Hz, (b) an amplitudebetween about 3 and 9 V, (c) a series of pulses having widths betweenabout 0.05 and 0.2 ms, and/or (d) a duration of about 20-45 seconds.

For some applications, the control unit is adapted to configure thewaveform to include a rise time lasting between about 1 second and 5seconds prior to attaining a designated waveform application voltage.Alternatively or additionally, the control unit is adapted to configurethe waveform to include a decay time lasting between about 1 second and5 seconds prior to returning to a baseline voltage.

For some applications, the control unit is adapted to configure thewaveform to have a duty cycle between about 50% and 100%. For someapplications, the control unit is adapted to configure the waveform tohave a duty cycle between about 6% and about 50%. For some applications,the control unit is adapted to configure the waveform to have a dutycycle of between about 2 and about 10 seconds on, and between about 10and about 30 seconds off.

There is further provided, in accordance with a preferred embodiment ofthe present invention, a method for implanting a medical device in apatient, including:

creating a suprapubic incision in the patient;

creating a vaginal mucosa incision in the patient;

passing between the two incisions an electrode lead which is adapted forcoupling to the medical device; and

implanting the medical device in the patient.

Preferably, implanting the device includes implanting a device which iscapable of treating a stress incontinence condition of the patient, anurge incontinence condition of the patient, an urge frequency conditionof the patient, a fecal incontinence condition of the patient, aninterstitial cystitis condition of the patient, a chronic pelvic paincondition of the patient, a neurogenic bladder condition of the patient,and/or a urine retention condition of the patient.

In a preferred embodiment, passing the electrode lead includessubcutaneously passing an inter-incision introducer between the twoincisions, and passing the electrode lead through the introducer. Inthis case, the method preferably also includes:

removing the inter-incision introducer, so as to leave an end of theelectrode lead accessible;

inserting a second introducer into the vaginal mucosa incision, suchthat a distal end of the second introducer is proximate a urethralsphincter site of the patient;

inserting the end of the electrode lead through the second introducer;and

securing the lead to the urethral sphincter site.

There is still further provided, in accordance with a preferredembodiment of the present invention, a device, including:

at least one electrode, which is adapted to be coupled to a pelvicmuscle of a patient; and

a control unit, which is adapted to drive the at Least one electrode toapply to the muscle an electrical waveform configured to treat aneurogenic bladder condition of the patient.

There is also provided, in accordance with a preferred embodiment of thepresent invention, a device, including:

at least one electrode, which is adapted to be coupled to a pelvicmuscle of a patient; and

a control unit, which is adapted to drive the at least one electrode toapply to the muscle an electrical waveform configured to treat anurgency frequency symptom of the patient.

The present invention will be more fully understood from the followingdetailed description of the preferred embodiments thereof, takentogether with the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic, pictorial view of an implantable device forprevention of mixed incontinence, in accordance with a preferredembodiment of the present invention;

FIG. 1B is a schematic, pictorial view of an implantable device forprevention of mixed incontinence, in accordance with another preferredembodiment of the present invention;

FIGS. 2A, 2B, 2C, 2D, 2E, 2F, and 2G show steps in an implantationprocedure of a stimulation device, in accordance with a preferredembodiment of the present invention;

FIG. 2H is a schematic, partly sectional illustration showingimplantation of the device of FIG. 1A in the pelvis of a patient, inaccordance with another preferred embodiment of the present invention;

FIG. 2I is a schematic, partly sectional illustration showingimplantation of the device of FIG. 1A in the pelvis of a patient, inaccordance with yet another preferred embodiment of the presentinvention;

FIG. 3 is a schematic block diagram illustrating circuitry used in animplantable muscle stimulation device, in accordance with a preferredembodiment of the present invention;

FIG. 4 is a schematic block diagram illustrating circuitry used in animplantable muscle stimulation device, in accordance with anotherpreferred embodiment of the present invention;

FIG. 5 is a schematic block diagram illustrating signal processingcircuitry for analyzing electromyogram signals, in accordance with apreferred embodiment of the present invention;

FIGS. 6-9 are graphs showing simulated and measured signals,representative of different aspects of use of an implantable musclestimulation device, in accordance with a preferred embodiment of thepresent invention;

FIG. 10A is a schematic diagram of a pressure sensor, in accordance witha preferred embodiment of the present invention; and

FIG. 10B is a schematic, sectional illustration of the bladder of apatient, showing implantation therein of the pressure sensor of FIG.10A, in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

I. Overview of Preferred Embodiments

-   -   A. General Description of Stimulator Device    -   B. Sensing and Control Functions of the Device    -   C. Signal Processing    -   D. Power Consumption Control

II. Detailed Description of Figures

-   -   A. External Elements of a Stimulator Device    -   B. Anatomical and Surgical Considerations    -   C. Signal Processing        -   (i) Hardware and Algorithms        -   (ii) Simulation of a Typical EMG        -   (iii) Experimentally Measured EMG Signals: Distinguishing            Incontinence from Voluntary Voiding    -   D. Muscle Stimulation    -   E. Provision of Power to the Control Unit    -   F. External Communication with the Control Unit    -   G. Utilization of Other Sensors    -   H. Reduction of Power Consumption        I. Overview of Preferred Embodiments

A. General Description of Stimulator Device

Various aspects of the present invention are described in this section(I) and in greater detail in the following section (II). As describedwith reference to the preferred embodiments shown in FIGS. 1A and 1B, anelectronic stimulator device is preferably implanted in the genitalregion of a patient who has at least two types of incontinence. Thedevice stimulates one or more of the muscles or nerves in the region, soas to control and treat the patient's incontinence. A preferred methodfor implanting the device is shown in FIGS. 2A, 2B, 2C, 2D, 2E, 2F, and2G.

Preferably, imminent urge or stress incontinence generates anelectromyographic (EMG) signal in the muscles, which is sensed by one ormore electrodes and is analyzed by a control unit of the device.Alternatively or additionally, non-electromyographic signals (e.g.,pressure signals) are received and analyzed by the control unit. Whenthe control unit determines that the signals are indicative of acondition that is likely to cause involuntary urine flow from thebladder, it applies an electrical waveform to the one or moreelectrodes, which is configured to treat the particular type ofincontinence detected (e.g., stress or urge), in order to stimulate apelvic muscle to contract and inhibit the urine flow. It is to beunderstood that although some preferred embodiments of the presentinvention are described herein with respect to interpreting EMG signalsso as to identify the onset of a particular condition, in many of theseembodiments, analysis of pressure signals or other non-EMG signals maybe performed instead of or in addition to the analysis of the EMGsignals.

B. Sensing and Control Functions of the Device

In addition to EMG sensing electrodes, the device preferably alsocomprises one or more other physiological sensors, described hereinbelowwith reference to FIGS. 2H, 2I, 3, 4, 10A, and 10B, which generatesignals responsive to, for example, motion, intravesical or abdominalpressure, or urine volume in the bladder. These signals are indicativeof some forms of incontinence.

Typically, when the urine volume in the bladder is low, there will be nourine flow even when the abdominal pressure does increase. As describedwith reference to a plurality of the figures, the control unitpreferably processes the signals from the various sensors and uses themto determine when the electrical stimulation should be applied to themuscles.

C. Signal Processing

Preferably, the control unit comprises a processor, e.g., as describedwith reference to FIGS. 3 and 4, which is additionally programmed todistinguish between signals indicative of possible incontinence andother signals that do not warrant stimulation of a nerve or muscle. Inparticular, the processor is preferably programmed to recognize signalpatterns indicative of normal voiding, and does not stimulate themuscles when such patterns occur, so that the patient can pass urinenormally. Detection of normal voiding is described in more detail withreference to FIGS. 7 and 8.

Preferably, the processor analyzes both long-term and short-termvariations in the signals, as well as rates, spectral patterns, andpatterns of change in the signals. For example, to inhibit stressincontinence, the processor may set a threshold of an aspect of the EMGsignal that varies over time responsive to an assessment of thepatient's physiological condition. Subsequently, the processor appliesthe stimulation only when a transient variation in the aspect of the EMGsignal exceeds the threshold. Methods for modifying the threshold inreal time are described with reference to FIG. 6.

In the context of the present patent application and in the claims, a“time-varying threshold” is to be understood as comprising substantiallyany appropriate time-varying detection parameters that a person skilledin the art, having read the disclosure of the present patentapplication, would consider useful in applying the principles of thepresent invention. By way of illustration and not limitation, thesetime-varying detection parameters may include magnitude, rate, or otheraspects of the EMG signal, or of quantitative ultrasound, pressure, oracceleration measurements, as described herein.

D. Power Consumption Control

As described with reference to FIG. 5, the control unit preferablycomprises a low-power, low-speed processor, which monitors the EMGand/or sensor signals continuously, and a high-speed processor, whichturns on only when the low-speed processor detects an increase in EMG orother activity. Use of the two processors has been shown tosignificantly reduce consumption of electrical power. The high-speedprocessor performs an accurate analysis of the signals to determinewhether stimulation is actually warranted.

Alternatively or additionally, the concepts described herein withrespect to two independent processors may be applied using a singleprocessor having two modes of operation—a low power, low capacity mode,and a high power, high capacity mode.

II. Detailed Description of Figures

A. External Elements of a Stimulator Device

Reference is now made to FIG. 1A, which is a schematic, pictorialillustration of an implantable electronic stimulator device 20, inaccordance with a preferred embodiment of the present invention. Device20 is preferably implanted in the pelvic region of a patient, asdescribed further hereinbelow, for use in providing muscle and/or nervestimulation so as to control and treat urinary urge and stressincontinence.

Device 20 comprises a control unit 22 and electrodes 27 and 29, coupledthereto by electrical leads 24. Additionally, device 20 preferablycomprises at least one additional physiological sensor 44, such as aminiature ultrasound transducer, one or more accelerometers, a pressuretransducer or other sensors known in the art.

The control unit preferably comprises circuitry for sensing electricalsignals received by electrodes 27 and 29, such as electromyogram (EMG)signals, along with circuitry for processing the signals from sensor 44.Control unit 22 additionally comprises circuitry for applying electricalstimulation waveforms to one or both of the electrodes responsive to thesignals. Details of control unit 22 and electrodes 27 and 29 arepreferably as described in the above-cited PCT Patent Publications WO00/19940, entitled “Incontinence Treatment Device,” and WO 00/19939,entitled, “Control of urge incontinence,” with appropriate changes asdescribed herein or as are otherwise indicated by clinical andengineering considerations that will be clear to those skilled in theart.

The electrodes are preferably flexible intramuscular-type wireelectrodes, about 1-5 mm long and 50-100 microns in diameter, thusdesigned to minimize patient discomfort. They are typically formed inthe shape of a spiral or hook, as is known in the art, so that they canbe easily and permanently anchored in the muscle. The wire from whichthe electrodes are made comprises a suitable conductive material,preferably a biocompatible metal such as silver, a platinum/iridiumalloy (90/10) or a nickel/chromium alloy. Leads 24 are preferably 5-10cm long and surrounded by an insulating jacket typically comprisingnylon, polyurethane, Teflon or another flexible, biocompatibleinsulating material. An optional additional wire (not shown) inside thejacket serves as an antenna for the purpose of wireless communicationswith device 20, as described further hereinbelow.

Control unit 22 preferably comprises circuitry for processing electricalsignals received from electrodes 27 and 29 and for applying a waveformto the electrodes. The circuitry is preferably contained in a case madeof titanium or other suitable biocompatible metal. Typically, the caseis about 20 mm in diameter and 4 mm thick. For some applications, thecase serves as a ground electrode for electrodes 27 and 29 when they aresensing or stimulating in a monopolar mode. Alternatively, the case maycomprise metal coated with a layer of biocompatible plastic, such aspolymethyl methacrylate (PMMA) or silicone. Although two electrodes andone sensor are shown attached to the control unit in FIG. 1A, it ispossible to use only a single electrode or, alternatively, additionalelectrodes and/or other sensors, as described further hereinbelow.

FIG. 1B is a schematic, pictorial illustration of electronic stimulatordevice 20, in accordance with another preferred embodiment of thepresent invention. Except with respect to the differences describedhereinbelow, the embodiment shown in FIG. 1B is generally similar to theembodiment shown in FIG. 1A, and techniques described herein withrespect to one of the configurations can generally be applied to theother configuration, mutatis mutandis.

A lead 21 is preferably provided to couple control unit 22 to a pelvicmuscle of the patient. Lead 21 is secured to the muscle by means of afixation helix 23 or other techniques known in the art, so as to provideelectrical contact between the muscle and two stimulation electrodes 26and 30 disposed on a silicon casing 19 of the lead. Each electrode istypically less than about 80 mm in length, and is most preferablyapproximately 3 mm in length. The electrodes are typically separated byapproximately 3 mm along the length of lead 21. In this space betweenelectrodes 26 and 30, a tip 15 of an EMG wire 17 may protrudeapproximately 100 microns through casing 19, for those applications inwhich EMG sensing is desirable. Typically, the diameter of wire 17 isapproximately 50 microns, and the diameter of casing 19 is approximately1.5 mm.

B. Anatomical and Surgical Considerations

FIGS. 2A, 2B, 2C, 2D, 2E, 2F and 2G show a method for implantation of apelvic stimulation device, in accordance with a preferred embodiment ofthe present invention. It is emphasized that although this implantationmethod represents a preferred method, other procedures, including thoseknown in the art, may also be adapted for use with other embodiments ofthe present invention. For illustrative purposes, the procedure is shownwhen performed upon a female patient. Unlike many implantationprocedures known in the art, the implantation procedure provided by thisembodiment is typically performed under local anesthesia, with thepatient placed in the lithotomy position. It will be appreciated thatthe surgical procedure shown in these figures has further benefits overmany similar prior art implantation procedures, in that the complicationrate resulting therefrom is significantly reduced by virtue of its beingcarried out in a region substantially devoid of major blood vessels, andin a manner that avoids risk to delicate structures.

FIG. 2A shows a 4 cm long “pocket” incision 170, made approximately 1 cmcephalad to the pubic bone in order to create a pocket in thesubcutaneous tissue adjacent to the fascia. A control unit will later beintroduced into this pocket.

FIG. 2B shows a vaginal mucosa incision 172. This second incision,approximately 0.5-1 cm long, is preferably made through the vaginalmucosa until the subcutaneous tissue, at a site approximately 0.5-1 cmanterior and lateral to the urethral meatus.

FIG. 2C shows the creation of a subcutaneous tunnel 174 using a 12 Frintroducer 176, placed in incision 172, and conveyed subcutaneouslyuntil it reaches and exits through incision 170.

FIG. 2D shows the insertion of a stimulation lead 178 through introducer176 until its exit at the lower end of the introducer.

FIG. 2E shows a stimulation lead tip 182 remaining outside incision 172after the removal of introducer 176.

FIG. 2F shows the reinsertion of stimulation lead 178 into incision 172.A 5 Fr splittable short introducer 180 is inserted into incision 172,adjacent to lead 178. The introducer is aimed slightly medially, i.e.,towards the urethra, care being taken not to injure the urethra.Introducer 180 is pushed for a distance of approximately 2.5 cm, to asite 0.5-1 cm lateral to the urethral wall. The free end of stimulationlead 178 is reinserted and advanced through short introducer 180 intothe urethral sphincter. Once the stimulation lead is properly secured,introducer 180 is withdrawn by being split into two parts. A 3/0 nylonsuture is made in the subcutaneous tissue around the stimulation lead.Subsequently, the free electrode lead is buried subcutaneously, andincision 172 is closed by a 3/0 plain catgut or Dexon suture.

An 8 Fr introducer (not shown) is inserted through incision 170, betweenthe fascia and muscle tissue, so as to reach the retropubic space. Asensor lead (not shown) for a pressure or electrical sensor is advancedthrough the introducer to a desired position, e.g., in the retropubicspace or between fascia and muscle. Following placement of the lead, itis secured to the fascia by a 3/0 nylon suture. Once the sensor has beenproperly secured, the lead stylet is withdrawn from the introducer, andthe introducer is then removed. Connectors for the sensor lead areconnected to appropriate sites on the control unit.

FIG. 2G shows the insertion of a control unit 184 through incision 170.After initial verification of the performance of the implanted system,incision 170 is closed with two layers.

FIG. 2H is a schematic, partly sectional illustration showing thegenitourinary anatomy of a female patient 31 in whom device 20 isimplanted, in accordance with another preferred embodiment of thepresent invention. It will be understood that, with appropriate changes,device 20 may be implanted in or coupled to a male patient. In thisembodiment, electrode 27 is inserted into a muscle 32, such as thelevator ani muscle, in a vicinity of urethra 34 and bladder 36.Electrode 29 is inserted into the patient's detrusor muscle 37, whichsurrounds bladder 36. Alternatively or additionally, electrodes 27 and29, or additional electrodes not shown in the figure, may be placed inor adjacent to other muscles of the pelvic floor.

The precise placement of the electrodes is typically not essential,particularly since electrical signals tend to pass among the differentmuscles in the region. Thus, any placement of the electrode in or on oneor more of the pelvic muscles suitable for exercising urine control isconsidered to be within the scope of this embodiment of the presentinvention. The electrodes are preferably inserted through an incisionmade in the wall of vagina 42. Alternatively, another suitable approachmay be chosen for ease of access and minimization of tissue trauma.

Control unit 22 is preferably implanted under the skin in thegenitopelvic region of patient 31. Most preferably, the control unit isimplanted inside the patient's labia minora 38 or in the labia majora40. Alternatively, the control unit is not implanted in the patient'sbody, but is instead maintained outside the body, connected by leads 24to the electrodes. This configuration is convenient particularly for aninitial test period, during which the effectiveness of device 20 intreating a given patient is evaluated before permanent implantation.

FIG. 2I is a schematic, partly sectional illustration showing thegenitourinary anatomy of patient 31 in whom device 20 is implanted, inaccordance with yet another preferred embodiment of the presentinvention. Preferably, control unit 22 is implanted in a vicinity of thesacral spine, as shown, but may alternatively be implanted in theabdomen or in the pelvis. According to this embodiment, the control unitdrives electrode 27 to stimulate a nerve that innervates one or moremuscles which are responsible for urine control. Typically, a sacralnerve is stimulated, so as to control the flow of urine from thebladder.

Generally, the choice of implantation location for the control unit, aswell as which particular nerve is to be stimulated, is made by thepatient's physician, responsive to the patient's condition and othersurgical considerations. Preferably, electrode 29 (FIG. 2H), isimplanted in the detrusor muscle or in another pelvic muscle, anddetects EMG signals, which are conveyed for analysis by the controlunit. Alternatively or additionally, bladder pressure and volume sensors(not shown) and electrode 29 convey signals to the control unitresponsive to bladder contractions associated with imminentincontinence, whereupon the control unit: (a) analyzes the signals todistinguish between aspects thereof indicative of stress incontinenceand aspects thereof indicative of urge incontinence, and (b) driveselectrode 27 to stimulate the sacral nerve and/or drives electrode 29 tostimulate the pelvic muscle, using stimulation parameters appropriatefor treating the identified form of urinary incontinence.

C. Signal Processing

(i) Hardware and Algorithms

FIG. 3 is a schematic block diagram showing circuitry used in controlunit 22 to receive signals from and apply electrical waveforms toelectrode 27, in accordance with a preferred embodiment of the presentinvention. Although in this embodiment device 20 is described asoperating in a monopolar mode, the principles described hereinbelow areapplicable to bipolar operation as well, in which both electrodes 27 and29 are active.

Electrode 27 receives EMG signals from muscle 32, which are conveyed viaa normally-closed switch 46 to the input of an amplifier 48, preferablya low-noise operational amplifier. Amplified signals output fromamplifier 48 are digitized by an analog/digital (A/D) converter 50 andconveyed to a central processing unit (CPU) 52, preferably amicroprocessor. Preferably, although not necessarily, the amplifiedsignals are not rectified prior to being digitized, to allow variousforms of analysis, for example, spectral analysis, to be performed onthe raw data, without the distortion imparted by rectification. CPU 52preferably analyzes these signals and/or signals from otherphysiological sensors, such as ultrasound, pressure, strain, andacceleration sensors described hereinbelow, to determine whether theyfit a pattern indicating that incontinence is likely to result, and, ifso, to determine the type of incontinence. The analysis preferablycomprises a spectral analysis and an analysis of EMG signal magnitudeand rate. Responsive to a determination that a particular form ofincontinence is likely, a pulse generator 54 conveys electrical pulsesto electrode 27, as described hereinbelow.

Optionally, sensor 44 (FIGS. 1A and 1B) comprises a miniaturizedultrasound transducer, which is implanted in proximity to bladder 36.Additionally or alternatively, sensor 44 comprises a pressure sensorfilled with silicon oil, as shown schematically in FIG. 10A. Furtheralternatively or additionally, sensor 44 comprises a pressure sensor inthe bladder, bladder wall, or elsewhere in the abdominal cavity; astrain sensor sutured to the bladder wall; or a sensor which detectsaction potentials in the bladder muscle. Most preferably, sensor 44comprises each of these. Signals from the transducer or sensor areconveyed to control unit 22 for analysis, particularly so as to enablethe control unit to estimate the urine volume within the bladder. Whenthe bladder is relatively empty, there is no need to actuate electrodes27 and 29, even when a transient increase in the electromyogram (EMG)signal or another signal would otherwise indicate an increasedprobability of imminent incontinence. Alternatively or additionally, theEMG signal itself may be analyzed to gain an indication of the urinevolume in the bladder, since when the bladder is full, the average EMGactivity typically increases. Further alternatively or additionally,analysis such as that described hereinbelow with reference to FIG. 9 maybe carried out, typically so as to determine the likelihood of imminenturge incontinence.

The CPU is preferably programmed to distinguish betweenincontinence-related patterns and other signal patterns not associatedwith incontinence, such as signals generated when patient 31 wishes topass urine voluntarily. Preferably, the CPU gathers long-termstatistical information regarding the EMG and the signals from the othersensors, and analyzes the information to “learn” common signal patternsthat are characteristic of patient 31. The learned patterns are used inrefining decision criteria used by the CPU in determining whether or notto apply waveforms to the electrodes. For some applications, a handheldcontroller (not shown) receives an input from the patient whenever urineis unintentionally passed, and control unit 22 modifies signal analysisparameters and/or stimulation parameters responsive thereto, so as toreduce the likelihood of future incontinence.

(ii) Simulation of a Typical EMG

FIG. 6 is a graph that schematically illustrates results of a simulationexperiment, in accordance with a preferred embodiment of the presentinvention, including a simulated EMG signal 100 of a woman sufferingfrom stress incontinence. A variable, adaptive threshold level 102 ismarked on the graph. Over the course of several hours, as the woman'sbladder fill level increases, the average level of EMG signal 100increases accordingly. In this example, threshold level 102 is computedso as to increase as a function of the average EMG. Alternatively oradditionally, threshold level 102 and a plurality of other time-varyingdetection parameters are calculated as functions of other features ofthe EMG signal or of other aspects of the woman's condition(particularly as measured by sensors 44, 76 and 78 (FIG. 4)), and areused separately or in combination in determining whether to applystimulation to inhibit involuntary urine flow. As shown, adaptivethreshold level 102 enables five possible incidents of incontinence,marked by excursions 104 of signal 100 over level 102, to be detectedreliably, with a low false alarm rate. On the other hand, if a fixedthreshold level 106 is used, as is known in the art, some EMG excursions104 are missed (at t=60 and 110 minutes), and, moreover, the false alarmrate is high (at t>220 minutes).

(iii) Experimentally Measured EMG Signals: Distinguishing Incontinencefrom Voluntary Voiding

FIG. 7 includes graphs 110 and 112 that schematically illustrateexperimental measurements made before, during and after voluntaryvoiding of urine, in accordance with a preferred embodiment of thepresent invention. Graph 112 is a continuation in time of graph 110. Theupper trace in both graphs illustrates urine flow, wherein the beginningand end of voluntary flow are marked by arrows. The lower traceillustrates measured EMG signals.

In a period preceding voiding, an EMG signal 114 shows substantialhigh-frequency activity, which is generally indicative of a fullbladder. High-frequency spikes in signal 114 (of which none appear inFIG. 7) would be interpreted by CPU 52 as signs of imminentincontinence, leading to actuation of pulse generator 54. On the otherhand, voluntary voiding is preceded by a portion 116 of the EMG signal,in which there is a large but gradual increase in the signal level. EMGsignal portion 116 is associated with voluntary activation of the pelvicfloor muscles for the purpose of passing urine from the bladder, as is alater signal portion 118 during the same act of voiding. Therefore, CPU52 preferably analyzes not only the level of the EMG signals, but also arate of change of the signals, in order to distinguish between voluntaryand involuntary contractions of the pelvic muscles. When the rate ofchange is characteristic of voluntary voiding, no stimulation is appliedby pulse generator 54.

FIG. 8 (not to scale) includes two graphs, showing: (a) data recordedduring a series of periods A, B, C and D, representing stages before,during, and after urination, and (b) preferred times with respect tothese periods for activation of pulse generator 54 in order to inhibiturge incontinence, in accordance with a preferred embodiment of thepresent invention. Bladder pressure data 140 and EMG data 150 shown inFIG. 8 are based on text and a figure in the above-referenced book,Urinary Incontinence (p. 35), which describes the voluntary voiding of ahealthy adult human female subject. Preferably, inputs to control unit22 include the EMG data and bladder pressure data, to enable the controlunit to determine an appropriate time to activate the pulse generator.

During period A, the bladder fills, which filling is preferably detectedand identified as such by the control unit. Notably, in period A thereis a slow, steady increase in bladder pressure, as well as a slow,steady increase in peak-to-peak amplitude of the EMG signal. Bladderpressure is seen to increase sharply during voiding period B, incomparison to the slow increase of period A. During period C, voidingwas terminated. During period D, the bladder fills again, insubstantially the same manner as in period A. Examination of periods Band C shows that the EMG signal has essentially zero magnitude duringvoiding and during its termination, and generally increases withincreasing bladder pressure during the bladder-filling periods A and D.

Preferably, control unit 22 identifies an initiation time of normalvoiding by analysis of the EMG and/or bladder pressure data. In apreferred embodiment, the control unit actuates pulse generator 54 toapply pulses to electrodes 27 and/or 29 at a predetermined time aftervoiding. For example, in an interview conducted during the calibrationperiod, it may be determined that a particular patient generally onlyexperiences urge incontinence greater than 1.5 hours following voluntaryvoiding. The control unit may then be programmed to detect voiding andinitiate pulse application one hour thereafter, and to continue thepulse application until a subsequent onset of voluntary voiding isdetected.

Alternatively or additionally, the pulse generator may be actuated bythe control unit when the average magnitude of the EMG exceeds aspecified threshold, because the likelihood of urge incontinencereflects the increased bladder pressure indicated by the EMG signalexceeding the threshold. Further alternatively or additionally, thecalibration period may include a training period, in which the controlunit continually samples the EMG signal, and in which the patientindicates to the control unit whenever urge incontinence occurs. Duringor subsequent to the training period, the control unit or an externalprocessor (not shown) analyzes each instance of urge incontinence todetermine aspects of the EMG and/or other sensor signals preceding theincontinence which can be used during regular operation of the unit topredict incontinence. For many applications of the present invention,the control unit is operative to execute some or all of the abovemethods, so as to minimize or eliminate occurrences of urgeincontinence. It will be appreciated that these strategies may beapplied to other types of incontinence as well, mutatis mutandis.

FIG. 9 is a graph showing simulated data, for use in detecting theimminent onset of urge incontinence, in accordance with a preferredembodiment of the present invention. Preferably, control unit 22analyzes a measured pressure-volume (or pressure-time) relationship ofthe patient's bladder, so as to determine whether the pressure isincreasing in a healthy manner, as represented by dashed line 130, orwhether it is characterized by one or more relatively sharp features132, which may indicate detrusor instability and imminent urgeincontinence. Preferably, if urge incontinence is deemed likely, thencontrol unit 22 initiates the stimulation of a pelvic muscle usingprotocols appropriate for treating the urge incontinence (describedhereinbelow), which are typically different from those suitable for thetreatment of stress incontinence. Measurement of bladder volume may beperformed using ultrasound techniques or by means of a strain gaugefixed to the patient's bladder. It is to be understood that whereas apressure-volume curve is shown in FIG. 9, a pressure-time curve maysimilarly be generated and subsequently interpreted to identifyanalogous sharp features indicative of imminent urge incontinence.

Alternatively or additionally, the patient is enabled to instructcontrol unit 22 to initiate electrical stimulation of the muscles inorder to inhibit urge incontinence which the patient senses may beimminent. For example, the patient may input the instruction to thecontrol unit by voluntarily tightening her abdominal muscles, which inturn causes measurable increases in abdominal pressure. Advantageously,the rate of increase of abdominal pressure generated by voluntarycontraction of the abdominal musculature is significantly smaller thanthat increase generated involuntarily, for example, during laughter.Typically, the patient can be taught in a single training session togenerate a detectable and distinguishable muscle contraction,appropriate for controlling device 20. For some applications, controlunit 22 comprises an external input unit, such as a keypad with buttonsdesignated for certain functions, e.g., “Inhibit urge incontinence now,”or “Inhibit stress incontinence now.”

In a preferred embodiment, stress incontinence and urge incontinence aredistinguished solely (or at least in part) responsive to differences ind(Pressure)/dt characteristic of the respective conditions. For example,values of dP/dt greater than a threshold value are interpreted as beingindicative of stress incontinence, while values of dP/dt less than thethreshold are interpreted as being indicative of urge incontinence.

D. Muscle Stimulation

With reference to FIG. 3, when possible stress incontinence is detected,CPU 52 opens switch 46 and drives pulse generator 54 to apply a suitableelectrical waveform to electrode 27 so as to stimulate muscle 32 tocontract and thereby inhibit the incontinence which was detected. Switch46 is opened in order to avoid feedback of the stimulation waveform toamplifier 48, and is closed again after the waveform is terminated. Inthe embodiment shown in FIG. 3, the waveform is applied to the electrodein a monopolar mode, whereby a case 25 of control unit 22 serves as thereturn (ground) electrode. (This mode can be used only when case 25comprises a conductive material. When control unit 22 has a plasticcase, at least two electrodes on one or more leads are generally needed,in order to administer bipolar stimulation.)

For some applications, as muscle 32 contracts, it closes off urethra 34,thus inhibiting the undesired urine flow. Preferably, the waveform isterminated and switch 46 is closed after a predetermined period of timehas passed, e.g., 0.5-1 second to treat stress incontinence and 10minutes to treat urge incontinence. Alternatively or additionally, thewaveform is terminated and switch 46 is closed if the patient voidsvoluntarily or other new data indicate that the expected incontinence isno longer likely. If possible incontinence is again detected at thispoint, the waveform is re-applied.

It will be appreciated that, depending on the particular application,one or more waveforms may be employed in the practice of variousembodiments of the present invention. For example, the waveform may bemonophasic or biphasic and may have a range of amplitudes, duty cyclesand/or frequencies. It has been found generally that pulse frequenciesin the range between 2 and 50 Hz are effective in engenderingcontraction of the levator ani and other pelvic muscles, but for someapplications it may be appropriate to use frequencies outside of thisrange. Certain preferred stimulation parameters are describedhereinbelow. It has been found generally that duty cycles of about 2 toabout 10 seconds on, and about 10 to about 30 seconds off (i.e., about6% to about 50%) are effective for treating conditions disclosed herein.

Preferably, but not necessarily, the same electrode or electrodes areused to treat both stress incontinence and urge incontinence; however,different stimulation parameters are utilized depending on theparticular form of incontinence which is immediately to be treated.Alternatively, at least one electrode is dedicated to treating aparticular form of incontinence, e.g., an electrode implanted so as tostimulate the sacral nerve may be driven by control unit 22 to applycurrent most suitable for treating urge incontinence.

As described hereinabove, the processor preferably identifies the formof incontinence based on particular physiological characteristicsdetected by the sensors, and control unit 22 applies an appropriatestimulation signal responsive thereto. For example, stress incontinencemay be detected using techniques described hereinabove with reference toFIGS. 6 and 7, and urge incontinence may be detected using techniquesdescribed with reference to FIGS. 8 and 9. In patients with mixedincontinence, these techniques are typically sufficient to reveal thesignificant differences between the two types of incontinence, e.g., theimpulsive pressure and/or EMG spikes in instances of stress incontinenceare generally not present in urge incontinence, while thepressure-volume and pressure-time features characteristic of detrusorinstability and urge incontinence are correspondingly not characteristicof stress incontinence.

For some applications, two sensors are implanted at different siteswithin the patient. These generate signals which, in combination, areanalyzed by control unit 22 so as to determine whether a stressincontinence event or an urge incontinence event is imminent. In apreferred configuration, one pressure sensor is coupled to measureintravesical pressure, while another pressure sensor is coupled tomeasure intra-abdominal pressure. Sharp increases in bladder pressurethat occur generally simultaneously with sharp increases in overallabdominal pressure are typically interpreted to be indicative ofpossible imminent stress incontinence, e.g., due to laughter. Bycontrast, increases in bladder pressure that are not accompanied byincreases in overall abdominal pressure are interpreted as beingindicative of imminent urge incontinence.

Responsive to a determination of imminent incontinence, and theidentification of the particular type of incontinence, the stimulationwaveform is preferably applied, typically comprising a bipolar squarewave having characteristics summarized in Table I. This table alsoindicates appropriate stimulation parameters for the treatment of otherdisorders, such as fecal incontinence, interstitial cystitis (IC),chronic pelvic pain, and urine retention, described hereinbelow. Forsome applications and some patients, other parameters may also be used.

TABLE I Stress and fecal Chronic pelvic incon. Urge event pain and ICUrine retention Amp. 3–9 V 0.5–5 V 1–4 V 3–9 V Freq. 40–50 Hz 5–15 Hz5–15 Hz 1–10 Hz Pulse width 0.05–1 ms 0.05–1 ms 0.05–0.2 ms 0.05–0.2 msDuration of 0.2–1 s 5–10 min 10–30 min 20–45 s signal (stress); 1–20 s(fecal incon.) Rise time to ~0 0–1 min 0–3 min 0–5 s peak amp. Decaytime ~0 0-1 min 0-3 min 0-5 s Optional bursts Bursts not used. 1-5 s on,2 s on, 2-10 s on, (Duty cycle) 20-60 s off. 20 s off. 10-30 s off.Typical Typical Typical duty cycle: duty cycle: duty cycle: 5-15% 5-15%6-50%

Thus, it is seen that in response to a determination of imminent stressincontinence, e.g., due to the patient sneezing, a high-power waveformis applied, typically having both a high amplitude and a high frequency.This form of stimulation is generally preferred in inhibiting the rapidonset of stress incontinence, as the stimulation develops significantmuscular contraction over a very short time period, so as to prevent theinvoluntary passing of urine. Shortly after the triggering event (e.g.,the sneeze) has finished, the stimulation is preferably removed, becausethe likelihood of imminent incontinence is diminished.

By contrast, imminent urge incontinence is typically more suitablytreated over a longer time period. For example, a signal may be appliedfrom the time that control unit 22 determines that urge incontinence isimminent until the control unit determines that the patient hasvoluntarily voided. Because of the nature of urge incontinence, i.e., itis characterized by the involuntary and undesired contraction of bladdermuscles, a lower energy waveform is applied to a spinal site and/or to apelvic floor muscle. This lower energy waveform is preferably configuredto induce a relaxation response of the muscle tissue of the bladder, andto thereby inhibit involuntary urination. Advantageously, since thetreatment of urge incontinence typically does not consume electricalpower at the same rate as the treatment of stress incontinence, thedrain on implanted batteries resulting from the treatment of urgeincontinence is typically low, allowing the appropriate waveforms to beapplied for significantly longer time periods than those useful fortreating stress incontinence.

For some applications, the waveform for treating urge incontinence isapplied in bursts, e.g., the waveform is applied for about 1-5 seconds,and then removed for about 20-60 seconds. Typically, the relativelyshort bursts are sufficient to provide the patient with protectionagainst incontinence during the inter-burst periods. Advantageously,such a protocol of waveforms in bursts further reduces the consumptionof electricity.

In a preferred embodiment, for example, when treating patients withsevere urge incontinence, it is beneficial to treat the urgeincontinence prophylactically, i.e., more frequently than when aparticular event of urge incontinence is imminent. In this embodiment,waveforms are typically applied automatically, at a fixed time aftervoluntary voiding and/or whenever bladder volume or pressure exceeds athreshold. Alternatively or additionally, for some patients, thetreatment for urge incontinence is applied substantially continuously.Preferably, but not necessarily, these continuous or very-frequent modesof treatment are applied in bursts, as described hereinabove.

For some urge incontinence treatment applications, it is beneficial toextend the initiation of the application of the waveform over a periodranging from several seconds to about one minute. Thus, for example, a10 Hz square wave may be increased to a designated waveform applicationvoltage of 2 V over a period of 2 seconds, which is generally fastenough to inhibit urge incontinence, without inadvertently providing asharp stimulus that might elicit unintentional voiding. When it isdesired to apply the waveform in intermittent bursts, the amplitude istypically held at the peak value for approximately 1-5 seconds, andsubsequently caused to decay over a period of several seconds. Anextended decay time is also believed by the inventors to inhibitinadvertently eliciting the sharp bladder contractions which in someinstances may bring about incontinence.

Although preferred embodiments of the present invention are generallydescribed herein with respect to control unit 22 distinguishing betweenstress incontinence and urge incontinence, and applying an appropriatetreatment responsive thereto, it is to be understood that otherdisorders may also be treated some of the techniques described herein,mutatis mutandis. Thus, for example, chronic pelvic pain andinterstitial cystitis are preferably treated using stimulationparameters shown in Table I. As in the treatment of stress or urgeincontinence, the patient herself is typically enabled to activatecontrol unit 22 to treat the condition. Alternatively or additionally,the control unit is programmed to apply an appropriate waveformresponsive to a determination of bladder volume (e.g., via an ultrasoundmeasurement), bladder pressure, and/or based on the time from lastvoiding. Voiding is preferably determined using techniques describedherein, such as measuring changes in abdominal pressure, or analyzingpelvic floor EMG data. Typically, interstitial cystitis and chronicpelvic pain are treated, like urge incontinence, using electric signalapplication parameters configured to induce relaxation of the bladder.

As shown in Table I, pathological retention of urine (a condition commonin patients with paraplegia) is preferably treated by the application toa pelvic floor muscle of a waveform configured to facilitate voiding.Preferably, the patient is enabled to enter a command into an externalcontroller whenever voiding is desired.

In a preferred embodiment of the present invention, fecal incontinenceis treated by the application of a waveform to a pelvic floor site or toa site in or adjacent to the anal sphincter of the patient. Typically,waveform parameters are generally similar to those for treating stressincontinence. Additionally, because fecal incontinence often accompaniesurinary incontinence, particularly stress incontinence, the sametechniques described herein for detecting the onset of stressincontinence (e.g., EMG or pressure measurements) are preferably adaptedfor use in detecting the onset of fecal incontinence.

In normal physiological functioning, an accumulation of feces in therectum causes afferent signaling that leads to involuntary smooth musclecontraction in the pelvic region and to voluntary contraction of thestriated muscle of the anal sphincter. These contractions of smooth andstriated muscle provide the control required to defer defecation until adesired time. For some patients, fecal incontinence is caused at leastin part by an impairment of the afferent signaling which should occurresponsive to an accumulation of feces.

Therefore, in a preferred embodiment of the present invention, controlunit 22 is adapted to enhance the functioning of this afferent pathway,in order to restore normal levels of smooth and/or striated musclecontractions, and, consequently, to restore fecal continence.Preferably, control unit 22 senses the pressure in the patient's rectum,or senses another parameter indicative of rectal filling, and driveselectrodes implanted in or near the patient's anal sphincter to apply asignal which generates (or amplifies) afferent signaling. Typically,this induced afferent signaling is sufficient to alert the patient tothe gradually increasing level of rectal filling, such that the patientwill naturally respond by tightening the striated muscle of the analsphincter. Often, the induced sensation is indistinguishable fromanalogous natural sensations experienced by healthy individuals.

Advantageously, smooth muscle contractions are also believed to occurresponsive to the induced afferent signaling, such that after a periodof weeks to several months, smooth muscle contractions are expected tosupplement the striated muscle contractions, and provide enhancedprotection against fecal incontinence.

For some applications, the magnitude, frequency, and/or duty cycle ofthe applied signal is configured to simulate the body's natural afferentsignaling patterns, i.e., to have lower values when the rectum is onlyslightly full, and to increase in value responsive to indications ofincreased rectal filling.

It is to be appreciated that preferred stimulation parameters aredescribed herein by way of illustration and not limitation, and that thescope of the present invention includes the use of waveforms comprising,for example, biphasic and/or monophasic components, a decaying squarewave, a sinusoid or sawtooth waveform, or any other shape known in theart to be suitable for stimulating muscle or nervous tissue. Generally,appropriate waveforms and parameters thereof are determined during aninitial test period of device 20, and are updated intermittently, eitherin a healthcare facility or automatically during regular use.

E. Provision of Power to the Control Unit

With reference to FIGS. 3 and 4, power is supplied to the elements ofcontrol unit 22 by a battery 56, which may comprise a primary battery(non-rechargeable) and/or a rechargeable battery. Alternatively, asuper-capacitor, as is known in the art, may be used to store andprovide the electrical power. If a rechargeable battery orsuper-capacitor is used, it is preferably recharged via an inductivecoil 58 or antenna, which receives energy by magnetic induction from anexternal magnetic field charging source (not shown) held in proximity tothe pelvis of patient 31. The magnetic field causes a current to flow incoil 58, which is rectified by a rectifier 60 and furnished to chargebattery 56. An optional coil 28, coupled to CPU 52 for the purpose ofwireless communications with device 20, may also be used for chargingthe battery.

Preferably, battery 56 comprises a standard battery, such as a lithiumbattery, having a nominal output of 3 volts. Most preferably, pulsegenerator 54 comprises a DC/DC converter, as is known in the art, and acapacitor, which is charged by the DC/DC converter to a constant,stepped-up voltage level regardless of the precise battery voltage,which may vary between 3.5 and 1.8 volts. The same DC/DC converter, oranother similar device, preferably supplies power to other circuitcomponents of control unit 22.

F. External Communication with the Control Unit

An inductive arrangement using coil 28 is preferably used to program theCPU, using an external programming device (not shown) with a suitableantenna. Alternatively, the programming device generates a modulatedmagnetic field to communicate with a receiver inside case 25, whichpreferably senses the field using a Hall effect transducer. Suchprogramming may be used, for example, to set an amplitude or duration ofthe stimulation waveform applied by pulse generator 54, or to set athreshold level or other parameters, according to which the CPUdistinguishes between electromyographic or other signals that areindicative of impending urge or stress incontinence and those that arenot (e.g., those that indicate voluntary voiding). Such programming maybe carried out by medical personnel or by the patient herself, who cansimilarly turn the implanted control unit on and off as desired bypassing a suitable magnet over her pelvis.

Although the circuit blocks in control unit 22 are shown as discreteelements, some or all of these blocks are preferably embodied in acustom or semi-custom integrated circuit device, as is known in the art.

G. Utilization of Other Sensors

FIG. 4 is a schematic block diagram illustrating a muscle stimulatordevice 120, in accordance with an alternative embodiment of the presentinvention. Device 120 is substantially similar to device 20, except forfeatures described hereinbelow. Device 120 comprises a control unit 74,which is coupled to electrodes 27 and 29. Electrode 29 also serves as asensing electrode, furnishing electromyographic signals via switch 46 toamplifier 48, as described hereinabove. Alternatively, electrodes 27 and29 may be coupled as differential inputs to amplifier 48. Pulsegenerator 54 applies the stimulation waveforms between electrodes 27 and29 in a bipolar mode.

In addition to or instead of the electromyographic signals received fromelectrode 29, CPU 52 preferably receives additional signals from otherphysiological sensors, such as an ultrasound transducer, a pressuresensor 76 and/or an acceleration sensor 78, or other types of strain andmotion measurement devices, as are known in the art. Pressure sensor 76is preferably implanted on or in bladder 36, so as to detect increasesin abdominal or intravesical pressure that may lead to involuntary urineloss. Similarly, acceleration sensor 78 is preferably implanted so as todetect bladder motion associated with hypermobility, which is similarlyassociated with urine loss. The additional signals from these sensorsare preferably analyzed by the CPU together with the electromyographicsignals in order to improve the accuracy and reliability of detection ofimpending incontinence.

An impedance sensor 79 is preferably used to measure the tissueimpedance between leads 27 and 29, using physiological impedancemeasurement techniques known in the art. During long-term use of device120 (or other such devices), fibrosis in the area of the implantedelectrodes tends to cause the impedance to increase, so that thestimulating current for a given applied voltage decreases. The impedancemeasured by sensor 79 is used as a feedback signal instructing CPU 52 toincrease the voltage, so that a generally constant level of stimulationcurrent is maintained.

FIG. 10A is a schematic illustration (not to scale) showing details of asensor 160 for measuring intravesical pressure, in accordance with apreferred embodiment of the present invention. Sensor 160 preferablycomprises a pressure-sensitive element such as a piezoelectric elementor a piezoresistive element 162. Element 162 is typically surrounded bysilicon oil 166 or a similar liquid, which, in turn, is contained withina flexible wall 164. Preferably, element 162 is connected by four leads168 to control unit 22. Leads 168 are preferably coupled in a Wheatstonebridge formation, such that pressure on wall 164 induces a change inresistance of piezoresistive element 162 which, in turn, is detected bycontrol unit 22. Typically, control unit 22 applies a voltage across twoof the leads, and senses and amplifies the voltage developed across theother two leads in order to ascertain the pressure being applied tosensor 160. In order to increase battery life, the voltage appliedacross the leads is preferably applied in short pulses (e.g., 50microseconds on, 30 milliseconds off).

FIG. 10B is a schematic illustration (not to scale) showing sensor 160implanted in the muscle wall of bladder 36, in accordance with apreferred embodiment of the present invention. Typically, one or moresensors 160 are implanted in or on the bladder wall or elsewhere in theabdominal cavity.

H. Reduction of Power Consumption

FIG. 5 is a schematic block diagram showing details of signal processingcircuitry 80 for use in device 20 or 120, in accordance with a preferredembodiment of the present invention. In order to detect impendingincontinence with adequate reliability, A/D converter 50 optimallysamples the EMG signals from the electrodes at 1000-5000 Hz, and CPU 52preferably performs a detailed analysis of the sample stream. Systemsfor incontinence control known in the art, operating at sample ratesbelow 1000 Hz, cannot adequately distinguish between signals that may beindicative of incontinence and those that are not. For the purpose ofsuch high-rate sampling, CPU 52 preferably comprises a low-power,software-programmable processor. If A/D converter 50 and CPU 52 were tooperate continuously, however, battery 56 would rapidly run down.Therefore, circuitry 80 comprises a low-power, low-resolution A/Dconverter 84 and hard-coded processing logic 86, which operatecontinuously at a low sampling rate, preferably at about 100-200 Hz.Input from amplifier 48 to A/D converter 84 is preferably rectified by arectifier 82.

In operation, A/D converter 50 and CPU 52 are normally maintained in astandby state, in which their power consumption is negligible. Whenlogic 86, operating at the low sampling rate, detects EMG signals thatmay be a precursor to incontinence, it signals A/D converter 50 to beginsampling at the high rate. In order not to lose significant data fromthe brief period before A/D converter 50 and CPU 52 turn on, signalsfrom A/D converter 84 are preferably stored in a cyclic (or first-infirst-out) queue 88, such as a delay line. The entire sequence of signaldetection and processing is estimated to take between 5 and 20 ms, up tothe point at which CPU 52 reaches a decision as to whether or not toactuate pulse generator 54. Pulse generation takes between 1 and 20 ms,with the result that contraction of the pelvic muscles begins within15-50 ms of an onset of increased EMG activity indicating impendingurine loss. Thus, urethra 34 is substantially closed off before anysignificant amount of urine can leak out.

As shown in FIG. 5, EMG inputs from electrodes 27 and 29 are preferablyamplified before processing in a dual-differential configuration, so asto afford enhanced sensitivity and reduced noise. Electrodes 27 and 29are coupled to respective differential preamplifiers 87 and 89, theoutputs of which are differentially amplified by amplifier 48.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and sub-combinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofthat are not in the prior art which would occur to persons skilled inthe art upon reading the foregoing description.

1. A device, comprising: at least one electrode, which is adapted to becoupled to a pelvic muscle of a patient; and a control unit, which isadapted to drive the at least one electrode to apply to the muscle anelectrical waveform configured to treat a neurogenic bladder conditionof the patient responsive to an amount of time elapsed since the patientlast voided his or her bladder.
 2. A device, comprising: at least oneelectrode, which is adapted to be coupled to a pelvic muscle of apatient; and a control unit, which is adapted to drive the at least oneelectrode to apply to the muscle an electrical waveform configured totreat an urgency frequency symptom of the patient responsive to anamount of time elapsed since the patient last voided his or her bladder.3. A device according to claim 1, wherein the control unit is adapted toreceive an input from the patient and to apply the waveform responsiveto the input.
 4. A device according to claim 1, wherein the at least oneelectrode comprises a single monopolar electrode.
 5. A device accordingto claim 1, wherein the at least one electrode comprises a pair ofbipolar electrodes.
 6. A device according to claim 1, wherein the atleast one electrode comprises a flexible intra-muscular electrode.
 7. Adevice according to claim 1, wherein the at least one electrode and thecontrol unit are adapted to be implanted in the body of the patient. 8.A device according to claim 1, wherein the control unit is adapted toconfigure the waveform so as to induce relaxation of a bladder muscle ofthe patient.
 9. A device according to claim 8, wherein the control unitis adapted to configure the waveform to have a frequency componentbetween about 5 and 15 Hz.
 10. A device according to claim 8, whereinthe control unit is adapted to configure the waveform to have anamplitude between about 1 and 4 V.
 11. A device according to claim 8,wherein the control unit is adapted to configure the waveform to includea series of pulses having widths between about 0.05 and 0.2 ms.
 12. Adevice according to claim 8, wherein the control unit is adapted toconfigure the waveform to have a duration of about 10-30 minutes.
 13. Adevice according to claim 8, wherein the control unit is adapted toconfigure the waveform to include a rise time lasting between about 1second and 3 minutes prior to attaining a designated waveformapplication voltage.
 14. A device according to claim 8, wherein thecontrol unit is adapted to configure the waveform to include a decaytime lasting between about 1 second and 3 minutes, prior to returning toa baseline voltage.
 15. A device according to claim 8, wherein thecontrol unit is adapted to configure the waveform to have a duty cyclebetween about 6% and about 50%.
 16. A device according to claim 8,wherein the control unit is adapted to configure the waveform to have aduty cycle of between about 2 and about 10 seconds on, and between about10 and about 30 seconds off.
 17. A device according to claim 2, whereinthe control unit is adapted to receive an input from the patient and toapply the waveform responsive to the input.
 18. A device according toclaim 2, wherein the at least one electrode comprises a single monopolarelectrode.
 19. A device according to claim 2, wherein the at least oneelectrode comprises a pair of bipolar electrodes.
 20. A device accordingto claim 2, wherein the at least one electrode comprises a flexibleintra-muscular electrode.
 21. A device according to claim 2, wherein theat least one electrode and the control unit are adapted to be implantedin the body of the patient.
 22. A device according to claim 2, whereinthe control unit is adapted to configure the waveform so as to inducerelaxation of a bladder muscle of the patient.
 23. A device according toclaim 22, wherein the control unit is adapted to configure the waveformto have a frequency component between about 5 and 15 Hz.
 24. A deviceaccording to claim 22, wherein the control unit is adapted to configurethe waveform to have an amplitude between about 1 and 4 V.
 25. A deviceaccording to claim 22, wherein the control unit is adapted to configurethe waveform to include a series of pulses having widths between about0.05 and 0.2 ms.
 26. A device according to claim 22, wherein the controlunit is adapted to configure the waveform to have a duration of about10-30 minutes.
 27. A device according to claim 22, wherein the controlunit is adapted to configure the waveform to include a rise time lastingbetween about 1 second and 3 minutes prior to attaining a designatedwaveform application voltage.
 28. A device according to claim 22,wherein the control unit is adapted to configure the waveform to includea decay time lasting between about 1 second and 3 minutes, prior toreturning to a baseline voltage.
 29. A device according to claim 22,wherein the control unit is adapted to configure the waveform to have aduty cycle between about 6% and about 50%.
 30. A device according toclaim 22, wherein the control unit is adapted to configure the waveformto have a duty cycle of between about 2 and about 10 seconds on, andbetween about 10 and about 30 seconds off.
 31. A device, comprising: asensor, which is adapted to generate a signal responsive to a state of apatient; at least one electrode, which is adapted to be coupled to apelvic site of the patient; and a control unit, which is adapted toreceive the signal, to analyze the signal so as to distinguish betweenan imminent stress incontinence event and an imminent urge event, and,responsive to analyzing the signal, to apply an electrical waveform tothe at least one electrode, wherein the control unit is adapted toconfigure the waveform so as to induce relaxation of a bladder muscleresponsive to analyzing the signal and determining that an urge event isimminent, and wherein the control unit is adapted to configure thewaveform to have a duty cycle between about 6% and about 50%.
 32. Adevice, comprising: a sensor, which is adapted to generate a signalresponsive to a state of a patient; at least one electrode, which isadapted to be coupled to a pelvic site of the patient; and a controlunit, which is adapted to receive the signal, to analyze the signal soas to distinguish between an imminent stress incontinence event and animminent urge event, and, responsive to analyzing the signal, to applyan electrical waveform to the at least one electrode, wherein thecontrol unit is adapted to configure the waveform so as to inducerelaxation of a bladder muscle responsive to analyzing the signal anddetermining that an urge event is imminent, and wherein the control unitis adapted to configure the waveform to have a duty cycle of betweenabout 2 and about 10 seconds on, and between about 10 and about 30seconds off.
 33. A device, comprising: a sensor, which is adapted togenerate a signal responsive to a state of a patient; at least oneelectrode, which is adapted to be coupled to an anatomical site of thepatient; and a control unit, which is adapted to receive the signal, toanalyze the signal so as to determine a likelihood of imminent patientpain due to interstitial cystitis, and, responsive to analyzing thesignal, to apply to the at least one electrode an electrical waveformconfigured to reduce patient pain due to interstitial cystitis, whereinthe control unit is adapted to configure the waveform to have a dutycycle between about 6% and about 50%.
 34. A device, comprising: asensor, which is adapted to generate a signal responsive to a state of apatient; at least one electrode, which is adapted to be coupled to ananatomical site of the patient; and a control unit, which is adapted toreceive the signal, to analyze the signal so as to determine alikelihood of imminent patient pain due to interstitial cystitis, and,responsive to analyzing the signal, to apply to the at least oneelectrode an electrical waveform configured to reduce patient pain dueto interstitial cystitis, wherein the control unit is adapted toconfigure the waveform to have a duty cycle of between about 2 and about10 seconds on, and between about 10 and about 30 seconds off.
 35. Adevice, comprising: a sensor, which is adapted to generate a signalresponsive to a state of a patient; at least one electrode, which isadapted to be coupled to an anatomical site of the patient; and acontrol unit, which is adapted to receive the signal, to analyze thesignal so as to determine a likelihood of patient pelvic pain, and,responsive to analyzing the signal, to apply to the at least oneelectrode an electrical waveform configured to reduce the patient pelvicpain, wherein the control unit is adapted to configure the waveform tohave a duty cycle between about 6% and about 50%.
 36. A device,comprising: a sensor, which is adapted to generate a signal responsiveto a state of a patient; at least one electrode, which is adapted to becoupled to an anatomical site of the patient; and a control unit, whichis adapted to receive the signal, to analyze the signal so as todetermine a likelihood of patient pelvic pain, and, responsive toanalyzing the signal, to apply to the at least one electrode anelectrical waveform configured to reduce the patient pelvic pain,wherein the control unit is adapted to configure the waveform to have aduty cycle of between about 2 and about 10 seconds on, and between about10 and about 30 seconds off.